Copper and phosphorus effect on residual embrittlement of irradiated model alloys and RPV steels after annealing

The dependence of the recovery of the transition temperature shift after annealing (475 °C, 100 h) on copper and phosphorus contents has been studied on irradiated reactor pressure vessel (RPV) materials. A set of model alloys with low nickel content, lower than 0.2 mass%, was used for the study. Copper and phosphorus contents were varied in a wide range: 0.005–0.99 and 0.002–0.039 mass%, respectively. Recovery efficiency has been estimated by the value of residual embrittlement after annealing, measured in terms of a shift in transition temperature (ΔT_K^res). A comparison of the results obtained on model alloys with data for VVER-440 RPV materials has also been carried out. Comparative analysis has confirmed the conclusion that ΔT_K^res is independent of phosphorus content while the effect of copper on ΔT_K^res is not significant for typical VVER-440 RPV materials with a typical range of Cu contents between 0.10 and 0.24 mass%. However, for model alloys with a wider range of copper content, copper mainly controls the value of ΔT_K^res.